1. Field of the Invention
This invention relates in general to vehicle brakes and in particular to a brake pad having defined abutment contact points.
2. Description of the Related Art
Most vehicles are equipped with a brake system for slowing or stopping movement of the vehicle in a controlled manner. A typical brake system for an automobile or light truck includes a disc brake assembly for each of the front wheels and either a drum brake assembly or a disc brake assembly for each of the rear wheels. The brake assemblies are actuated by hydraulic or pneumatic pressure generated when an operator of the vehicle depresses a brake pedal. The structures of these drum brake assemblies and disc brake assemblies, as well as the actuators therefore, are well known in the art.
A typical disc brake assembly includes a rotor which is secured to the wheel of the vehicle for rotation therewith. A caliper assembly is slidably supported by pins secured to an anchor bracket. The anchor bracket is secured to a non-rotatable component of the vehicle, such as the vehicle frame. The caliper assembly includes a pair of brake shoes which are disposed on opposite sides of the rotor. The brake shoes are operatively connected to one or more hydraulically actuated pistons for movement between a non-braking position, wherein they are spaced apart from opposed axial sides or braking surfaces of the rotor, and a braking position, wherein they are moved into frictional engagement with the opposed braking surfaces of the rotor. When the operator of the vehicle depresses the brake pedal, the piston urges the brake shoes from the non-braking position to the braking position so as to frictionally engage the opposed braking surfaces of the rotor and thereby slow or stop the rotation of the associated wheel of the vehicle.
The brake pad includes a pair of ear portions that project outwardly from a main portion of the brake pad. Each of the ear portions are disposed within respective grooves formed in each respective anchor bracket. The ear portions are typically square or rectangular shaped as are the receiving grooves in the anchor bracket. Gaps are formed between the sides of each ear portion and the respective receiving grooves. The locations of contact between the sides of each ear portion and respective receiving grooves, as well as the gaps, vary due to tolerances in the components and variations in the installation and assembly of the vehicle brakes.
When the brakes are applied, as described above, the piston urges the brake pads into contact with the braking surface of the rotor. As the brake pads contact the braking surface of the rotor, the induced torque biases the braking pad in a forward direction (i.e., same direction as the rotation of the respective wheel). This, in turn, will cause each of the ear portions to move within its respective groove in the direction of the applied torque. Each ear will transition from a non-braking contact abutment point(s) to a braking contact abutment point(s) within the respective groove. The braking abutment contact points vary from brake pad to brake pad because the originating non-braking contact abutment point(s) are not the same, as discussed above.
In a braking system having noise, vibration, and harshness (NVH) concerns, one of the factors which causes difficulty in pinpointing the source of the NVH concern is when contact abutment surfaces between a respective ear portion and a respective groove vary from one brake pad to the next. If the variations in contact locations between the brake pads were to be eliminated—that is, the abutment surfaces had abutment contact surface repeatability—NVH concerns originating from the braking shoes would be easier to diagnose.